1. The Field of the Art
The present invention relates to an apparatus for driving an air core gauge of the type having a pair of coils in quadrature to generate a resultant magnetic field in accordance with electric currents applied thereto and having a pointer angularly swept by the magnetic field to indicate an input quantity.
2. Description of the Related Art
In Japanese Patent Publication No. 60-368, there has been proposed an apparatus which is arranged to apply to coils a pair of driving signals which vary in phase by 90.degree.. The relationship between the currents applied to the coils and the sweep angle of the pointer is defined by a signal having an isoceles trapezoid waveform. The length in the bottom side of the isoceles trapezoid waveform is longer in comparison to the length of the opposite side of the isoceles trapezoid waveform by a ratio of 2.29. This ratio results in an isoceles trapezoid waveform which approaches waveform of a sine or cosine function. It is, however, observed that corner waveform portions of the isoceles trapezoid waveform have steep bending points causing sudden and large changes. These changes result in faulty gauge readings. For this reason, there is an inherent drawback. The pointer is angularly swept in a breathing mode to give disharmonious feelings to an observer.